Speed sensitive limited slip differential

Abstract

A speed sensitive limited slip differential having a sealed, self contained clutch actuator which expands and retracts as required to frictionally seat a clutch element against a surface of the differential casing. The clutch actuator comprises a housing portion and a piston portion which define two fluid chambers and a gerotor pump assembly contained therein for transferring fluid between the two fluid chambers. The gerotor pump assembly is splined to an output element to transfer fluid between the two chambers when sufficient differential rotation between the output element and the casing exists. The transfer of fluid between the two chambers results in the axial expansion of the actuator housing and the actuator piston to provide an axial force on a side gear to thereby frictionally seat the clutch element against a surface of the differential casing. The sealed, self contained feature allows the present limited slip differential to operate in a simple, reliable manner.

What is claimed is: 
     
       1. A limited slip differential, comprising: a rotatable casing;   a pinion gear rotatably supported in said casing;   a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear;   a clutch disposed in said casing on one axial side of said side gear and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear; and   a sealed clutch actuator disposed in said casing on the opposite axial side of said side gear, said clutch actuator having a fluid pressure source contained therein, said fluid pressure source transferring fluid in response to differential rotation between said side gear and said casing, said clutch actuator urging said clutch to move and to frictionally seat against said rotatable casing in response to transfer of fluid by said fluid pressure source.   
     
     
       2. The limited slip differential of claim 1, wherein said sealed clutch actuator expands axially with respect to said rotatable casing in response to a transfer of fluid by said fluid pressure source. 
     
     
       3. A limited slip differential comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a sealed clutch actuator disposed in said casing, said clutch actuator having a fluid pressure source contained therein, said fluid pressure source transferring fluid in response to differential rotation between said side gear and said casing, said clutch actuator urging said clutch to move and to frictionally seat against said rotatable casing in response to transfer of fluid by said fluid pressure source, wherein said sealed clutch actuator comprises a clutch actuator housing and a clutch actuator piston, said clutch actuator piston disposed around said output element, said clutch actuator housing disposed around said clutch actuator piston, said clutch actuator housing and said clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by said fluid pressure source, whereby fluid transfer from one said fluid chamber to another said fluid chamber by said fluid pressure source causes said clutch actuator housing and clutch actuator piston to move in opposite directions. 
     
     
       4. The limited slip differential of claim 3, wherein said clutch actuator housing is rotationally fixed with respect to said casing by anti-rotation pins disposed in recesses of said clutch actuator housing and said casing, said clutch actuator piston is rotationally fixed with respect to said casing by anti-rotation pins disposed in recesses of said clutch actuator piston and said casing. 
     
     
       5. The limited slip differential of claim 4, wherein said clutch actuator piston includes a bypass orifice in fluid communication between said first and second fluid chambers, whereby fluid flow through said bypass orifice equalizes fluid pressure between said first and second fluid chambers. 
     
     
       6. A limited slip differential comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, a sealed clutch actuator disposed in said casing, said clutch actuator having a fluid pressure source contained therein, said fluid pressure source transferring fluid in response to differential rotation between said side gear and said casing, said clutch actuator urging said clutch to move and to frictionally seat against said rotatable casing in response to transfer of fluid by said fluid pressure source, and a transfer block disposed between said side gear and said clutch, said transfer block transmitting axial force from said side gear to said clutch. 
     
     
       7. A limited slip differential comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a sealed clutch actuator disposed in said casing, said clutch actuator having a fluid pressure source contained therein, said fluid pressure source transferring fluid in response to differential rotation between said side gear and said casing, said clutch actuator urging said clutch to move and to frictionally seat against said rotatable casing in response to transfer of fluid by said fluid pressure source, wherein said clutch comprises a frusto-conical surface adapted to seat against a complementary frusto-conical surface disposed on said casing. 
     
     
       8. A limited slip differential comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, a sealed clutch actuator disposed in said casing, said clutch actuator having a fluid pressure source contained therein, said fluid pressure source transferring fluid in response to differential rotation between said side gear and said casing, said clutch actuator urging said clutch to move and to frictionally seat against said rotatable casing in response to transfer of fluid by said fluid pressure source, and a second side gear and a second output element, said second side gear rotatably supported in said casing and coupled to said second output element, said second side gear meshingly engaged with said pinion gear, said second side gear coupled with said clutch, wherein said second side gear transmits axial force to said clutch. 
     
     
       9. A limited slip differential comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a sealed clutch actuator disposed in said casing, said clutch actuator having a fluid pressure source contained therein, said fluid pressure source transferring fluid in response to differential rotation between said side gear and said casing, said clutch actuator urging said clutch to move and to frictionally seat against said rotatable casing in response to transfer of fluid by said fluid pressure source, wherein said fluid pressure source is a gerotor type pump. 
     
     
       10. The limited slip differential of claim 9, wherein said gerotor type pump comprises an impeller disposed inside an internal gear, said impeller coupled to said output element. 
     
     
       11. A limited slip differential, comprising: a rotatable casing;   a pinion gear rotatably supported in said casing;   a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear;   a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear; and   a clutch actuator disposed in said casing, said clutch actuator comprising a clutch actuator housing and a clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by a fluid pressure source, said fluid pressure source transferring fluid from one of said fluid chambers to another said fluid chamber in response to differential rotation between said side gear and said casing, said clutch actuator housing and said clutch actuator piston adapted to move with respect to said casing to urge said clutch to frictionally seat against said casing in response to transfer of fluid by said fluid pressure source.   
     
     
       12. A limited slip differential, comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a clutch actuator disposed in said casing, said clutch actuator comprising a clutch actuator housing and a clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by a fluid pressure source, said fluid pressure source transferring fluid from one of said fluid chambers to another said fluid chamber in response to differential rotation between said side gear and said casing, said clutch actuator housing and said clutch actuator piston adapted to move with respect to said casing to urge said clutch to frictionally seat against said casing in response to transfer of fluid by said fluid pressure source, wherein said clutch actuator housing is rotationally fixed with respect to said casing by anti-rotation pins disposed in recesses of said clutch actuator housing and said casing, said clutch actuator piston is rotationally fixed with respect to said casing by anti-rotation pins disposed in recesses of said clutch actuator piston and said casing. 
     
     
       13. A limited slip differential, comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a clutch actuator disposed in said casing, said clutch actuator comprising a clutch actuator housing and a clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by a fluid pressure source, said fluid pressure source transferring fluid from one of said fluid chambers to another said fluid chamber in response to differential rotation between said side gear and said casing, said clutch actuator housing and said clutch actuator piston adapted to move with respect to said casing to urge said clutch to frictionally seat against said casing in response to transfer of fluid by said fluid pressure source, wherein said clutch actuator piston includes a bypass orifice in fluid communication between said first and second fluid chambers, whereby fluid flow through said bypass orifice equalizes fluid pressure between said first and second fluid chambers. 
     
     
       14. A limited slip differential, comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, a clutch actuator disposed in said casing, said clutch actuator comprising a clutch actuator housing and a clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by a fluid pressure source, said fluid pressure source transferring fluid from one of said fluid chambers to another said fluid chamber in response to differential rotation between said side gear and said casing, said clutch actuator housing and said clutch actuator piston adapted to move with respect to said casing to urge said clutch to frictionally seat against said casing in response to transfer of fluid by said fluid pressure source, and a transfer block disposed between said side gear and said clutch, said transfer block transmitting axial force from said side gear to said clutch. 
     
     
       15. A limited slip differential, comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a clutch actuator disposed in said casing, said clutch actuator comprising a clutch actuator housing and a clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by a fluid pressure source, said fluid pressure source transferring fluid from one of said fluid chambers to another said fluid chamber in response to differential rotation between said side gear and said casing, said clutch actuator housing and said clutch actuator piston adapted to move with respect to said casing to urge said clutch to frictionally seat against said casing in response to transfer of fluid by said fluid pressure source, wherein said clutch comprises a frusto-conical surface adapted to seat against a complementary frusto-conical surface disposed on said casing. 
     
     
       16. A limited slip differential, comprising a rotatable casing, a pinion gear rotatably supported in said casing, a side gear rotatably supported in said casing and coupled to an output element, said side gear meshingly engaged with said pinion gear, a clutch disposed in said casing and operatively coupled to said side gear, said clutch adapted to frictionally transfer torque between said casing and said side gear, and a clutch actuator disposed in said casing, said clutch actuator comprising a clutch actuator housing and a clutch actuator piston defining first and second fluid chambers, said first and second fluid chambers fluidly connected by a fluid pressure source, said fluid pressure source transferring fluid from one of said fluid chambers to another said fluid chamber in response to differential rotation between said side gear and said casing, said clutch actuator housing and said clutch actuator piston adapted to move with respect to said casing to urge said clutch to frictionally seat against said casing in response to transfer of fluid by said fluid pressure source, wherein said fluid pressure source is a gerotor type pump. 
     
     
       17. The limited slip differential of claim 16, wherein said gerotor type pump comprises an impeller disposed inside an internal gear, said impeller coupled to said output element.